1. Technical Field
The present disclosure relates to a display device and a light guide device.
2. Related Art
Devices that use diffraction elements such as holographic elements include, for example, hologram recording and playback devices, and display devices that guide image light by using diffraction elements so as to enter the eyes of a user. In holographic elements, the pitches of interference patterns are optimized so as to obtain the highest diffraction efficiencies at predetermined wavelengths. As a light source, for example, a semiconductor laser may be used. However, even if a semiconductor laser operates in a single mode, the laser beam has a certain spectrum width, and light beams of wavelengths other than a predetermined wavelength may affect the resolution. Furthermore, wavelengths of light emitted from a semiconductor laser may vary due to ambient temperatures and other factors, and such variations may also affect the resolution. To solve the problem, for example, JP-A-2000-338847 proposes a structure in which a holographic element that absorbs wavelengths other than a predetermined wavelength is provided in a prior stage of a diffraction element such as a holographic element.
If optical components such as a mirror and a lens are disposed between two diffraction elements to reduce the size of the device, increase the degree of freedom of design, and correct various aberrations, depending on the directions of the two diffraction elements, beams of light having wavelengths other than a predetermined wavelength may become incident on positions notably beyond the original target point, and such deviation may affect the resolution.